The present invention relates in general to the field of optic communications, and in particular, to a method of integrating a pigtailed CMOS receiver with a CMOS-compatible optical bench, and a device manufactured using the method.
Optical transceivers are key components in fiber-optic communication systems. They transmit and receive photonic signals to and from high-speed fiber-optic cables and convert them from and to electronic signals for transmission through non-optical portions of networks and terminal equipment. Low-cost fiber-optical transceivers are now being developed by a number of companies for fiber-optic LAN and data communications markets. The key components in such transceivers include: the transmitter and/or detector device, the driver and/or receiver electronics, and an efficient means for packaging these components together with the optical fiber.
A promising method of making such devices is the Silicon Optical Bench (SiOB) technology described in Bell Labs Research, Dept. BL01-1144, Silicon Optical Bench-GOLD CD ""97, March, 1997. This technology provides the ability to etch V-grooves to hold optical wave guide fibers and direct the light to and from the ends of the fibers. Typically, this SiOB technology is then packaged on a second level board that holds the detector and/or laser chips as well as the receiver and/or laser driver electronics. In some cases, an active alignment is needed to align the fiber with the laser because each sits on a separate substrate.
Reducing the number of surfaces and components is a way to reduce the cost and package complexity of optoelectronic (OE) transceivers. To achieve this goal, the prior application disclosed a method of attaching OE devices such as a GaAs light-detector and a light-modulator on a pre-fabricated silicon CMOS IC. The attachment is preferably done using the well-known flip-chip bonding technique, which provides about 1 xcexcm alignment accuracy between the OE device and the VLSI circuit, especially when performing reflow after bonding. Despite these advances in the art, a need still exists for a reduction in the number of surfaces and components in order to further reduce the cost and packaging complexity of OE transceivers.
As used in this application, a fiber-optic xe2x80x9cpigtailxe2x80x9d is a short optical fiber, typically used to connect fiber optic components such as lasers and couplers.
In one aspect, the present invention is directed toward a fully integrated monolithic hybrid optoelectronic (OE) chip that combines electronic circuits, optical devices that are either flip-chip bonded or surface mounted on the electronic circuits, and fibers. In another aspect, the electronic circuits include a CMOS detector and receiver; or a CMOS transmitter and driver.
In another aspect, the present invention is a technique for attaching fibers to CMOS circuits with a silicon-based detector and receiver to create a fully integrated CMOS receiver for multimode fiber application at 850 nm. The integrated silicon detector and CMOS receiver can serve as a cheap power/signal monitor (for low speed applications) or even a high-speed Gigabit/s detector if the CMOS detector is designed appropriately.
In a first preferred embodiment, the invention is directed toward a fully integrated hybrid monolithic optoelectronic (OE) device comprising: a substrate including: a first CMOS circuit formed on the substrate; a groove, formed within the substrate and in suitable optical alignment with the first CMOS circuit; a second CMOS circuit formed on the substrate; a fiber-optic pigtail of sufficient length communicatively coupling the first CMOS circuit with the second CMOS circuit; and an optical fiber disposed within the groove and affixed to the substrate, wherein the optical fiber is cleaved and coated with a metal to form an angled, mirrored surface. In another aspect, the first CMOS circuit comprises a photodetector and the second CMOS circuit comprises a receiver, or the first CMOS circuit comprises a phototransmitter and the second CMOS circuit comprises a driver. In a yet another aspect, the optical fiber is cleaved at an angle greater than 42xc2x0. In a further aspect, the optical fiber is cleaved at an angle sufficient to impart total internal reflection to light emerging from the optical fiber.
In a yet another aspect, the invention is directed toward a fully integrated hybrid monolithic OE device for use in a CMOS color camera; a Local Area Network; for operation in the near-infrared region; at a wavelength of about 850 nm;
In another aspect, the invention is directed toward a fully integrated OE device comprising a light guiding structure such as a ball lens.
In a second preferred embodiment, the invention is directed toward a method of forming a hybrid OE device upon a substrate comprising the steps of forming a first CMOS circuit on the substrate; forming a receiving groove in the substrate such that the receiving groove is in a desirable alignment relative to the first CMOS circuit; disposing an optical fiber within the groove; securing the optical fiber within the groove; cleaving and coating the optical fiber to form an angled, mirrored surface; forming a second CMOS circuit on the substrate; and coupling the second CMOS circuit with the first CMOS circuit with a pigtail connection of sufficient length; wherein a photonic path is formed from the optical fiber to the first CMOS circuit, and an optical path is formed between the first CMOS circuit and the second CMOS circuit. In another aspect, the first CMOS circuit is an optical detector and the second CMOS circuit is a receiver; or the first CMOS circuit is an optical transmitter and the second CMOS circuit is a driver.